The invention relates to imaging output materials. In a preferred form it relates to the use of a laminated fabric base material for silver halide and ink jet images.
It is known to create images on fabric, with paintings on canvas and screen printing fabric. It has been desired to obtain the look of an image on fabric using silver halide imaging and inkjet printing.
Prior art methods of generating photographic quality images on fabric are time consuming and costly. The photographer prints the silver halide image on regular silver halide imaging paper and carefully peels the emulsion layer off the paper support. It can take several tries, ruining many images, before the emulsion is peeled off of the support in one piece. The emulsion layer is then glued onto a fabric and placed in a press where pressure is applied to the emulsion and fabric so the emulsion takes on the surface characteristics of the fabric. This long and involved process is the reason for the high prices of photographic xe2x80x9ccanvasxe2x80x9d prints.
The use of inkjet printing techniques to print on textiles has met with several problems. First, and in spite of the large number of inkjet inks currently available, inkjet printed images on textiles are often of low quality. For example, the printed images often smear upon handling, exhibit bleed (the intrusion of one color into an adjacent color), are moisture sensitive, and are dull, i.e., colored inks when printed fail to accurately produce the expected hues. Moreover, the printed images are often neither water-fast nor detergent-resistant, resulting in fading of the printed image after washing. Printed textile images with these drawbacks are wholly unacceptable to the textile industry, which requires not only that the image be both water-resistant and detergent-resistant, but also that the colors and hues are those deemed acceptable in the textile field. In addition, the textile industry also demands that while the colorant of the ink must adhere tenaciously to the substrate, it also must not alter the desirable hand properties of the substrate. This combination of requirements is very difficult to accomplish. Furthermore, fabrics tend to have loose fibers that clog the inkjet print head causing plugged nozzles and degraded imaged quality.
Prior art imaging elements are typically glossy and have a low surface roughness. The desired approach for typical imaging elements is to reduce the roughness of the base by providing a thick polymer coating on paper or laminate the paper with a high modulus biaxially oriented polymer sheet. U.S. Pat. No. 5,866,282 (Bourdelais et al) provides a method for reducing the roughness of paper by lamination of 0.22 micrometer cellulose paper with high modulus biaxially oriented polymer sheets. The resulting imaging element is smooth and very low in surface roughness.
U.S. Pat. No. 6,300,053 (Fujiwara et al.) relates to a photothermographic element where the support could be fabric. This fabric could be coated with a polymer. While the photothermographic imaging element does provide an acceptable image, the surface replication of the fabric is too low to provide the look and feel to the image. High surface replication fabric imaging elements are desirable in that they provide a unique look and feel that allows commercial display imaging to use texture to provide a look consistent with images that have a high textural content such as clothing, animals and upholstery.
U.S. Pat. No. 6,143,480 (Obayashi at al.) relates to a leuco dye and image recording medium wherein the base could be a non-woven fabric. U.S. Pat. No. 6,297,001 (Takiguchi et al.) relates to thermally developable photosensitive materials where the base could be fabric or cotton fabric. In this patent, the fabric is not polymer coated or sized, the fabric has a tendency to absorb the dye making the image less saturated. In the present invention, the fabric is protected form the imaging element by a polymeric sheet keeping the entire imaging element at the surface of the structure creating a saturated image.
U.S. Pat. No. 6,291,150 (Camp et al.) relates to a fabric as a base in a laminated structure for a silver halide imaging element. While the fabric base does provide a fabric image, the replication of the fabric is low and does not yield the desired look and feel of a differentiated imaging element. Fabrics disclosed have low roughness as the intent was to provide glossy image elements.
U.S. Pat. No. 5,749,092 (Arrington) relates to a polymer/glass matrix of polymer and glass fibers for use as a photographic support for increased stiffness. While the glass fiber does provide increased strength, the glass fiber is not woven into a pattern and thus does not add the desired textural appeal.
U.S. Pat. No. 6,245,710 (Hare et al.) relates to an imaging transfer system and process for transferring a thermal recording image to a receptor element where the receptor element is fabric. The fabric receiving element is not polymer coated or sized making the image less saturated because the fabric has a tendency to absorb the dye.
There is a need to provide a textural quality to high quality images while at the same time not interfering with image formation.
The invention provides an imaging element comprising at least one image layer and a base wherein said base comprises an upper polymer sheet having an elastic modulus of between 500 and 6,000 MPa said upper sheet being adhered to a textile having a roughness of between 0.8 and 8.0 micrometers, and a lower polymer sheet adhered to said textile.
The invention provides an imaging element that has the look and feel of a textural fabric material. The invention also provides the bi-directional strength and fire resistance to the imaging element.
It has been found that a composite material consisting of a textile and polymer sheet to form a base for an imaging elements such as ink jet receiver layers or light sensitive silver halide imaging systems, eliminates some of the issues surrounding printing with imaging directly onto fabric while still maintaining the look and feel of fabric. By separating the imaging layer and the fabric with a laminated a plastic film the imaging layer takes on the texture of the film, but the imaging layer does not penetrate the film. Because the imaging chemistry is concentrated at the top of the imaging element, the image has higher chroma and is more saturated. With an environmental protection film placed over the image, the image is also water and detergent-fast. The laminated structures also prevent stray fibers from the fabric from clogging inkjet heads or contaminating silver halide developing chemistry. In the case of a silver halide print, the processing steps of striping the emulsion layer and reattaching it to a cloth could be eliminated by using the silver halide laminated fabric image. The silver halide image would be formed directly onto the laminated fabric with the desired surface texture.
The texture and feel of fabric is valued for commercial printing, portraits and painting re-prints. The texture and feel of the fabric material is difficult to reproduce using prior art cellulose paper fiber base material which tend to yield smooth continuous surfaces. Further, the textile imaging element of the invention provides a significant strength improvement compared to paper base imaging systems allowing the invention material to be used for commercial printing, sails, furniture slip covers, cat scratch post, and wall coverings.
Woven fabrics that are made from thermoplastic yarns tend to disassemble along the cut edge when cut and subsequently handled. This disassembly occurs as the result of the untangling of the warp and weft yarns and is commonly known as raveling. Raveling significantly reduces the efficiency of subsequent article handling operations such as winding and unwinding and shipping and seriously reduces the strength of the fabric at its edges. Various physical procedures have been proposed and adopted to prevent edge raveling. These include fusing the warp and weft yarns along the cut edge by various means during the cutting process. Processes known to be commonly used in this regard are based on hot-die slitting and laser cutting methods. Generally, these methods are unacceptably slow or add significant costs to the production of the finished article.
The invention uses ultrasonic cutting to cut and seal the edge of the imaging support using fabric as the support material. The ultrasonic slitting method slits and seals in one step the thermoplastic fabric, laminates, and polymer films together to prevent edge penetration due to silver halide photo finishing. These and other advantages will be apparent from the detailed description below.
xe2x80x9cTextilexe2x80x9d and xe2x80x9cfabricxe2x80x9d means any knit, woven or spun-bonded fabric utilizing long fibers or yarns containing mono-filaments or multiple filaments. Cellulose paper materials consisting of short fibers that are formed on a wire are excluded from this definition. Examples of yarn materials include cotton, denim, polyacrylics, polyamides, polyesters, polyolefins, rayons, wool, linen, jute, sisal, regenerated cellulosic fibers such as rayon or cellulose acetate, leather, and combinations thereof. The fabric may be constructed of natural, synthetic or polymer fibers such as cotton, rayon, polyester, polyamide, polyacrylic and the like. Preferred fabrics are constructed from polyester fibers and blends of such fibers either in the individual yarns or in combinations of different yarns. The yarns employed to produce the textile fabric substrate may also be continuous filaments or spun yarns. As used herein the term xe2x80x9cnonwoven fabricxe2x80x9d means a web having a structure of individual fibers or threads which are interlaid, but not in an identifiable manner as in a woven fabric. Woven textile are those having continuous fibers with crosswise threads alternatively under and over lengthwise threads. Nonwoven fabrics or webs have been formed by many processes such as for example, meltblowing processes, spunbonding processes, and bonded-carded-web processes.
xe2x80x9cFiberxe2x80x9d is any natural or synthetic fiber, in continuous filament or staple form, which may be spun, knitted, woven, pressed or otherwise formed into a textile material or fabric, including silks, cottons, wool, leather, fur, alpaca, llama, camel, cashmere, angora, vicuna, guanaco, other animal hair, kapok, linen, flax, jute, manila, alfa, coconut, broom, ramie, sisal, polyesters, acetates, triacetates, rayon, rayon-acetates, cellulose, polypropylene-cellulose, alginates, cupro (regenerated cellulose), modal, regenerated protein fiber, polyacryl, polychloride, fluorofiber, modacryl, polyacrylonitrile, polyamide (including nylon), polyethylene, polypropylene, polyurea, polyurethane, vinylal, trivinyl, elastodiens, elasthane, and mixtures of these natural and synthetic fibers, among others.
The terms as used herein, xe2x80x9ctopxe2x80x9d, xe2x80x9cupperxe2x80x9d, xe2x80x9cimage receiving layer sidexe2x80x9d, and xe2x80x9cfacexe2x80x9d mean the side or toward the side of the fabric carrying the image or image receiving layer. The terms xe2x80x9cbottomxe2x80x9d, xe2x80x9clower sidexe2x80x9d, and xe2x80x9cbackxe2x80x9d mean the side or toward the side opposite of the imaging layers or the imaging receiving layers.
The surface roughness or Ra is a measure of surface irregularities or textures of a surface. For the invention, the roughness average, Ra, is the sum of the absolute value of the difference of each discrete data point from the average of all the data divided by the total number of points sampled. The textile has a surface roughness of 0.8 to 8.0 micrometers. When the surface roughness of the textile is less than 0.6 micrometers, the textile roughness approaches the roughness of paper and the textile structure can not be detected through the image. When the surface roughness average is greater than 10.0 micrometers, puddling of the emulsion or dye receiving layers occurs creating density differences across the imaging element. Puddling occurs on a rough surface when the emulsion fills in the large and deep valleys in the surface texture creating differences in the thickness of the image layer coating and thus differences in density across the imaging element. Most preferred is a textile with a surface roughness of between 4.0 and 6.0 micrometers. It has been shown that this range of average surface roughness for textiles creates a textile look for the imaging element without puddling.
The upper polymer sheet has an elastic modulus, also known as Young""s modulus, of between 500 and 6,000 MPa. Below 450 MPa the polymer sheet replicates the surface roughness of the fabric to too great an extent and causes puddling of the imaging layer. For example, if a textile had a surface roughness of 4 microns and a polymer sheet that had an elastic modulus of 300 Mpa was applied to the surface of the textile, the surface roughness of the textile with the polymer sheet would be essentially the same as the original textile sheet and puddling would occur. Above 7,000 MPa, the polymer sheet will not replicate the surface roughness of the textile enough to give the desired textile look. The polymer sheet would be too stiff to follow the roughness of the textile and instead cover it over making the imaging element smooth. Most preferably, the upper polymer sheet has an elastic modulus of between 800 and 4,000 MPa. It has been shown that with the elastic modulus in the range, the roughness of the textile is maximized for the textile look, while puddling is avoided.
In the imaging element of the invention the suitable thickness of the textile is between 75 and 750 micrometers. When the textile is thinner than 60 microns or thicker than 850 microns it has been shown that the imaging element is difficult to handle in conventional printing processes, such as silver halide and inkjet. When the textile is too thin, the imaging element lacks stiffness and will not transport correctly though the processing machinery. When the textile is too thick, the imaging element becomes too thick to transport though processors and becomes difficult for slitting and sealing the edges.
Preferably, the textile has less than 2 millimeters of edge penetration during image processing. When silver halide photographic support is processed, the chemicals penetrate the slit edges of the support to a measured width and leave a stain of the chemicals. Over 3.5 millimeters of edge penetration is readily visible to the observer""s eye and customers find the edge staining objectionable. As the edge penetration increases, it can sometimes be viewed not only on the back of the support (opposite side form the imaging element), but can be seen through the imaging layer if the stain is dark and the image is light colored at the edges. An edge penetration of less than 2 millimeters is generally not seen by the consumer.
Preferably, the textile comprises a woven polymer. The woven polymer could be any polymer fibers that could be woven giving the imaging element strength and durability. The woven polymer could be, but is not limited to polyolefins, polyesters, polyamides, polycarbonates, cellulosic esters, polystyrene, polyvinyl resins, polysulfonamides, polyethers, polyimides, polyvinylidene fluoride, polyurethanes, polyphenylenesulfides, polytetrafluoroethylene, polyacetals, polysulfonates, polyester ionomers, and polyolefin ionomers. Copolymers and/or mixtures of these polymers can be used.
Furthermore, when the imaging element is slit or cut, if ultrasonic slitting is applied, the textile can melt with the polymer sheets forming a solid plastic barrier to edge penetration of chemistry. Woven polymers are easily processed, widely available, and have a wide range of roughness of the woven texture.
A textile of woven fiberglass is preferred in some embodiments. Fiberglass is tough and fireproof making it ideal for signage and displays. Woven fiberglass also adds stiffness to the imaging element. Additionally, the woven fiberglass can be incased easily in a matrix of polymer, which could be a fire retardant and sizing agent, to create a fire resistant and non-absorbing textile for the imaging element. This adjunct bond between the fabric and polymer matrix is strengthened because the resin will flow to a certain extent into the interstices of the glass fabric and cover the overlaps of the weft and warp knuckles of the cloth. The fabric itself is thus strengthened by the resin coating.
The fabric comprising a fire retardant is preferred. Convention Halls have requirements about the display materials used in the shows because of the great fire hazard if the display materials are flammable. Having fire resistant fabrics is also necessary for children""s clothing, wallpaper, and tents. Having the fire retardant in the fabric can create fire resistant printed textile products that do not need a separate fire retardant treatment after processing because it is built into the fabric.
Most preferably, the fire retardant is a brominated aliphatic compound provided such compounds have at least one hydrogen atom attached to a carbon atom that is adjacent to a carbon atom containing at least one bromine atom. Brominated aliphatic compounds provide exemplary fire resistance and are easily incorporated into synthetic polymer fabrics. Representative brominated aliphatic compounds include, but are not limited to, hexabromocyclododecane; tris (2,3-dibromopropyl)phosphate; tetrabromo-vinylcyclohexene; tetrabromocyclooctane; pentabromo-chlorocyclohexane; 1,2-dibromo-methyl)cyclohexane; hexabromo-2-butene; and 1,1,1,3-tetrabromononane. Particularly preferred brominated aliphatic flame retardant compounds include hexabromocyclododecane and its isomers, pentabromocyclohexane, and its isomers. Other suitable brominated fire retardant compounds include tribromodiphenyl ether, tetrabromodiphenyl ether, pentabromodiphenyl ether, hexabromodiphenyl ether, tribromochlorodiphenyl ether, tribromodichlorodiphenyl ether, trichlorodiphenyl ether, tetrabromodichlorodiphenyl ether, octobromodiphenyl ether, decabromodiphenyl ether, the 2-ethylhexyl, n-octyl, nonyl, butyl, dodecyl and 2,3-dioxypropyl ethers of tribromophenyl, tribromochlorophenyl, tribromodichlorophenyl, tetrabromobisphenol A, dioctyl ester of tetrabromophthalic acid. The fire retardant may comprise a mixture of one or more brominated fire retardants. The brominated fire retardant preferably comprises between about 0.2 and about 10.0 and more preferably between about 0.6 and about 2.5 weight percent elemental bromine based upon the total weight of thermoplastic material in the composite structure.
Textile and fabric comprising hollow fibers is preferred in some embodiments. The hollow fibers give strength to the textile and also impart a different look to the material. As the light passes through the textile and is reflected back through the image to create a reflection print, the light is reflected at different points in the hollow fiber in the air void center of the fiber. These different reflection planes of the surface of the fiber and the inside air core of the fiber create a nacreous appearance to the reflected image. Materials for such a hollow fiber used are polymers such as cellulose, cellulose acetate, polyamide, polyacrylonitrile, ethylene-vinylalcohol copolymer, poly(methyl methacrylate) and polysulfone. Among these, hollow fiber membranes comprising a polysulfone resin are superior in heat resistance, chemical resistance, mechanical strength, biological compatibility and the like.
In another embodiment of the invention, textiles comprising a fabric of cotton, silk, sisal, wool, flax, or other natural fibrous material are preferred. Using natural fibers is preferred because the imaging element has more of the fabric feel to the image. Printed clothing or other apparel can be created using natural fibers as the textile. Furthermore, different natural fibers or mixtures thereof can be used to impart different characteristics to the imaging element.
The bottom polymer sheet preferably is provided with indicia. The bottom biaxially oriented polyolefin sheet preferably is reverse printed such that when the bottom biaxially oriented polyolefin sheet is laminated to the voided polyester base with the printed side laminated to the voided polyester, the indicia is protected from photographic processing chemistry and consumer handling. The indicia may be one or more colors and may be applied by any method known in the art for printing on biaxially oriented sheets. Examples include gravure printing, off set lithography printing, screen printing and ink jet printing.
Preferably, the upper polymer sheet generally replicates the surface of the textile. Most preferred is an 80% replication of the textile surface by the upper polymer sheet. This means that the roughness average of the polymer sheet with laminated to the textile is at least 80% of the surface roughness average of the textile. Replication of the textile surface by the upper polymer sheet gives the imaging element the textile look while protecting the fabric from processing chemistry and keeping the imaging layer on the surface of the imaging element making it more saturated. Without replication of the textile, the imaging element would be flat and smooth and not appear to be a textile texture. Replication of at least 80% insures that the texture is replicated in the polymer sheet to achieve the textile look.
To model upper polymer replication of the textile, represent system as a supported beam (upper polymer sheet) at each end (by peaks of texture of textile) with a distributed load across the beam. The maximum deflection of the upper polymer sheet in the y (vertical) direction is:
y=5PL3/384EI
where P is the applied load, L is the length of the span, E is the elastic modulus of the beam and I is the moment of inertia of the beam. The moment of inertia is defined by
I=bh3/12
Where b is the width if the beam an h is the thickness of the beam. Substituting into the deflection equation
y=60PL3/384Ebh3
Using dynamic similitude, the length of the beam, the modulus of the beam, the width of beam along with the coefficient 60/384 can be replaced by a constant, k. The deflection y will be converted to a ratio of replication R where
R=MPEfinal/MPEinitial
Thus, the equation for deflection becomes
R≅KP/h3
Since the effects of P are not known, the equation reduces to
R≅K/h3
(P is mostly inversely proportional to R) From the traces R=100/1000=0.1. Solving for K knowing h=35.6 micrometers, K=4.50*10xe2x88x929 cm3. The object is to find an h (thickness of the upper polymer layer) where R (ratio of replication) is zero. Plugging in R=0.001 (almost no replication) into the equation, h=165 micrometers. This means that when the upper polymer layer is 165 micrometers or greater, there is essentially no replication of the textile surface underneath (assuming that the approximations in the model are true).
For the upper polymer sheet, suitable classes of thermoplastic polymers for the upper sheet comprise polyolefins and polyesters. Suitable polyolefins include polypropylene, polyethylene, polymethylpentene, polystyrene, polybutylene and mixtures thereof. Polyolefin copolymers, including copolymers of propylene and ethylene such as hexene, butene, and octene are also useful. Polypropylene is preferred, as it is low in cost and has desirable strength properties.
In another embodiment of the invention, polyester is preferred because it has improved resistance to tearing. Suitable polyesters include those produced from aromatic, aliphatic or cycloaliphatic dicarboxylic acids of 4-20 carbon atoms and aliphatic or alicyclic glycols having from 2-24 carbon atoms. Examples of suitable dicarboxylic acids include terephthalic, isophthalic, phthalic, naphthalene dicarboxylic acid, succinic, glutaric, adipic, azelaic, sebacic, fumaric, maleic, itaconic, 1,4-cyclohexanedicarboxylic, sodiosulfoisophthalic and mixtures thereof. Examples of suitable glycols include ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, 1,4-cyclohexanedimethanol, diethylene glycol, other polyethylene glycols and mixtures thereof. Such polyesters are well known in the art and may be produced by well-known techniques, e.g., those described in U.S. Pat. No. 2,465,319 and U.S. Pat. No. 2,901,466. Preferred continuous matix polyesters are those having repeat units from terephthalic acid or naphthalene dicarboxylic acid and at least one glycol selected from ethylene glycol, 1,4-butanediol and 1,4-cyclohexanedimethanol. Poly(ethylene terephthalate), which may be modified by small amounts of other monomers, is especially preferred. Other suitable polyesters include liquid crystal copolyesters formed by the inclusion of suitable amount of a co-acid component such as stilbene dicarboxylic acid. Examples of such liquid crystal copolyesters are those disclosed in U.S. Pat. Nos. 4,420,607; 4,459,402; and 4,468,510.
The bottom sheet is preferably adhered to the textile or fabric with a pressure sensitive adhesive. The pressure sensitive adhesive could be permanent or repositionable. The pressure sensitive adhesive must provide excellent adhesion between the textile and the bottom sheet for the useful life of the image. The preferred method of adhering the textile and the bottom sheet is by use of an adhesive. The adhesive preferably is coated or applied to the base sheet. The adhesive preferably is a pressure sensitive adhesive or heat activated adhesive. During the bonding process, the imaging layer is adhered to the base by use of a nip roller or a heated nip roll in the case of a heat activated adhesive. A preferred pressure sensitive adhesive is an acrylic-based adhesive. Acrylic adhesives have been shown to provide an excellent bond between gelatin developed imaging layers and biaxially oriented polymer base sheets.
The preferred adhesive materials may be applied using a variety of methods known in the art to produce thin, consistent adhesive coatings. Examples include gravure coating, rod coating, reverse roll coating and hopper coating. The adhesives may be coated on the biaxially oriented sheets of this invention prior to lamination or may be used to laminate the biaxially oriented sheets to the textile.
The lower polymer sheet that comprises a release layer for said adhesive that repositions is preferred. The release layer allows for uniform separation of the adhesive at the adhesive substrate interface. The release layer may be applied to the substrate by any method known in the art for applying a release layer to substrates. Examples include silicon coatings, tetrafluoroethylene flurocarbon coatings, fluorinated ethylene-propylene coatings and calcium stearate.
As used herein, the phrase xe2x80x9cphotosensitive silver halidexe2x80x9d is a material that utilizes photosensitive silver halide in the formation of images. The imaging element where at least one image layer is formed using photosensitive silver halide is preferred because of the superior image quality of silver halide images and the abundance of exposing and processing infrastructure available in the world. Silver halide is also a very cost effective way of creating high quality images. The photographic elements can be black and white, single color elements or multicolor elements. Multicolor elements contain image dye-forming units sensitive to each of the three primary regions of the spectrum. Each unit can comprise a single emulsion layer or multiple emulsion layers sensitive to a given region of the spectrum. The layers of the element, including the layers of the image-forming units, can be arranged in various orders as known in the art. In an alternative format, the emulsions sensitive to each of the three primary regions of the spectrum can be disposed as a single segmented layer.
At least one imaging layer formed by ink jet printing, is preferred. The ink-jet type printing apparatus holds various advantages in that an ink-jet head can be made compact easily, high definition image can be printed at high speed, a running cost is low, a noise level is low for non-impact type printing, and a multi-color printing employing a plurality of colors of inks can be done easily. Furthermore, because inkjet is a digital system, each image can be different.
The ink used in the invention usually contains a colorant such as a pigment or dye. Suitable dyes include acid dyes, direct dyes, water soluble dyes or reactive dyes listed in the COLOR INDEX but is not limited thereto. Metallized and non-metallized azo dyes may also be used as disclosed in U.S. Pat. No. 5,482,545, the disclosure of which is incorporated herein by reference. Other dyes which may be used are found in EP 802246-A1 and JP 09/202043, the disclosures of which are incorporated herein by reference.
Any of the known organic pigments can be used to prepare ink jet inks used in the invention. Pigments can be selected from those disclosed, for example, in U.S. Pat. Nos. 5,026,427; 5,085,698; 5,141,556; 5,160,370 and 5,169,436, the disclosures of which are hereby incorporated by reference. The exact choice of pigment will depend upon the specific color reproduction and image stability requirements of the printer and application. For four-color printers, combinations of cyan, magenta, yellow and black (CMYK) pigments are used. An exemplary four color set is a cyan pigment, bis(phthalocyanylalumino)-tetraphenyldisiloxane, quinacridone magenta (pigment red 122), pigment yellow 74 and carbon black (pigment black 7).
The imaging element comprising a sizing polymer is preferred. The sizing polymer prevents edge penetration of water and silver halide process chemistry into the support and therefore eliminates the delamination of the polymer sheets and the textile and eliminates the stain occurring from edge penetration of the silver halide developing solution.
Preferably, the sizing polymers contain latex polymers. Latex polymers are not water soluble and have good adhesion to the fabric therefore creating a good seal on the cut end of the fabric against edge penetration. Examples of other commercially available water-insoluble polymers are: Carboset.RTM.1086, a poly(styrene/acrylic acid/2-ethylhexyl acrylate) latex, available from B.F. Goodrich Co., Akron, Ohio; Basoplast.RTM.250D, a latex of poly(acrylonitrilelbutyl acrylate), available from BASF Corporation, Charlotte, N.C.; Jetsize.RTM.Plus, a cationic poly(styrene/acrylate) latex, available from Eka-Nobel, Marietta, Ga.; Flexbond.RTM.381, poly(ethylene/vinyl acetate) latex, available from Air Products Corporation, Allentown, Pa.,; and Flexbond.RTM.325, poly(ethylene/vinyl acetate) latex, available from Air Products Corporation.
The sizing agent selected from the group consisting of alkoxysilanes, polyvinyl alcohol, polyvinyl acetate, aqueous epoxies and aqueous polyurethanes is preferred. These sizing polymers are very effective and easily applied and have excellent adhesion to fabric. These polymers fill and coat the fabric and fill in the gaps creating a barrier to water or chemistry penetration. The sizing agents may be used either singly or in combination. Conventional processes for treatment of sizing materials include screen printing, knife coating, padding, and the like.
An upper environmental protection layer over the image layer is preferred. The ability to provide the desired property of post-process water/stain resistance of the imaged element, at the point of manufacture of the imaging element, is a highly desired feature. However, in order to accomplish this feature, the desired imaging element should be permeable to aqueous solutions during the processing step, but achieve water impermeability after processing, without having to apply additional chemicals or to substantially change the chemicals used in the processing operation.
The environmental protection layer provides a discontinuous polymer overcoat to the imaging side of imaging elements, particularly photographic paper. The discontinuous polymer overcoat of the invention, while allowing a normal exposure and processing step, also provides a continuous, water-impermeable protective layer by using a post-process coalescing step, without substantial change or addition of chemicals in the processing step. The overcoat is formed by coating in a discontinuous manner an aqueous or volatile solvent solution comprising a dispersible or soluble polymer, or a polymer melt on the emulsion side of a sensitized photographic product. After exposure and processing, the product with image is subjected to a fusing step, wherein it is treated in such a way as to cause coalescence of the coated polymer patches, by heat and/or pressure, solvent treatment, or other means so as to form the desired continuous, water impermeable protective layer. In a preferred embodiment the polymer comprises a combination of low and high Tg polymers to enable post-process melt flow and coalescence during the fusing step. While it is well known to apply such combinations of polymers, in a continuous manner to elements bearing an image, the application of the same on an imaging element, during its manufacture, prior to any image formation will only work if the overcoat is applied in a discontinuous manner. Otherwise the flow from the low Tg component will cause coalescence prior to processing to give a continuous processing solution impermeable overcoat.
Examples of polymer solutions/dispersions used in this invention are derived can be selected from, for example, polymers of alkyl esters of acrylic or methacrylic acid such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, ethyl acrylate, butyl acrylate, hexyl acrylate, n-octyl acrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, nonyl acrylate, benzyl methacrylate, the hydroxyalkyl esters of the same acids such as 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, and 2-hydroxypropyl methacrylate, the nitrile and amides of the same acids such as acrylonitrile, methacrylonitrile, and methacrylamide, vinyl acetate, vinyl propionate, vinylidene chloride, vinyl chloride, and vinyl aromatic compounds such as styrene, t-butyl styrene and vinyl toluene, dialkyl maleates, dialkyl itaconates, dialkyl methylene-malonates, isoprene, butadiene, chlorinated propylene and copolymers therof. Suitable polymers containing carboxylic acid groups include polymers derived from acrylic monomers such as acrylic acid, methacrylic acid, ethacrylic acid, itaconic acid, maleic acid, fumaric acid, monoalkyl itaconate including monomethyl itaconate, monoethyl itaconate, and monobutyl itaconate, monoalkyl maleate including monomethyl maleate, monoethyl maleate, and monobutyl maleate, citraconic acid, and styrene carboxylic acid. Other polymers include ethyl cellulose, nitrocellulose, linseed oil-modified alkyd resins, rosin-modified alkyd resins, phenol-modified alkyd resins, phenolic resins, polyesters, poly(vinyl butyral), polyisocyanate resins, polyurethanes, polyamides, chroman resins, dammar gum, ketone resins, maleic acid resins, poly(tetrafluoroethylene-hexafluoropropylene), low-molecular weight polyethylene, phenol-modified pentaerythritol esters, copolymers with siloxanes and polyalkenes. These polymers can be used either alone or in combination. The polymers may be crosslinked or branched.
The upper polymer sheet comprising a layer of biaxially oriented microvoided polymer sheet where the microvoided polymer sheet comprises a series of microvoids separated by polymer matrix in the vertical direction such that said microvoided polymer sheet when reflecting light has an opalescent appearance is preferred. This microvoided upper polymer layer provides a photograph having an opalescent appearance particularly in the light areas, without a need for changing the chemistry of the imaging layers. The photographs of the invention are particularly desirable for use in photographs that will be displayed as they are eye-catching and unique. The photographs of the invention will also particularly appeal to children, as the metallic sheen and opalescent surface will attract their attention.
Preferably, the seal between the upper and lower polymer sheets prevent edge penetration. If the textile is not sealed with the polymer sheets and not protected in another way, the textile can act as a wick for developing chemistry pulling it inside the imaging element structure. This developing solution stains the support (textile) and can be seen on the backside of the support. The stain can also be seen through low density areas of the image. Edge penetration also causes delamination of the polymer films to the textile causing fraying and splitting edges.
The seal between the upper and lower polymer sheets has burst strength of at least 5 N. If the burst strength between the upper and lower polymer sheets is less than 3 N the seal could be broken during transport, handling, and processing and could create breaks in the seal and allow edge penetration to occur. Furthermore, if the burst strength is less than 3 N then consumer handling could break the seal and cause delamination of the edges and fraying of the fabric.
U.S. Pat. No. 3,697,357 discloses welding sheets made entirely or partially of thermoplastic material or fiber by sealing an area of material. U.S. Pat. No. 3,939,033 discloses using ultrasonics to simultaneously seal and cut thermoplastic textile material. U.S. Pat. No. 5,061,331 discloses an ultrasonic cutting and edge sealing apparatus for cutting and sealing semi-permeable and at least partially thermoplastic fabric.
In acoustic bonding or welding, such as ultrasonic welding, two parts to be joined (typically thermoplastic parts) are placed directly below an ultrasonic horn. In plunge bonding or welding, the horn plunges (travels toward the parts) and transmits ultrasonic vibrations into the top part. The vibrations travel through the top part to the interface of the two parts. Here, the vibrational energy is converted to heat due to intermolecular friction that melts and fuses the two parts. When the vibrations stop, the two parts solidify under force, producing a weld at the joining surface.
Continuous ultrasonic welding is typically used for sealing fabrics, films, and other parts. In the continuous mode, typically the ultrasonic horn is stationary and the part is moved beneath it.
Many uses of ultrasonic energy for bonding and cutting thermoplastic materials involve ultrasonic horns. A horn is an acoustical tool usually having a length of a multiple of one-half of the horn material wavelength and made of, for example, aluminum, titanium, or steel that transfers the mechanical vibratory energy to the part. (Typically, these materials have wavelengths of approximately 25 cm (10 in).) Horn displacement or amplitude is the peak-to-peak movement of the horn face. The ratio of horn output amplitude to the horn input amplitude is termed gain. Gain is a function of the ratio of the mass of the horn at the vibration input and output sections. Generally, in horns, the direction of amplitude at the face of the horn is coincident with the direction of the applied mechanical vibrations.
The invention uses ultrasonic cutting to cut and seal the edge of the imaging support using fabric as the support material. The ultrasonic slitting method seals the thermoplastic fabric, laminates, and polymer films together to prevent edge penetration due to silver halide photo finishing and other aqueous solutions. With ultrasonic slitting, the sheet is cut and the edges are sealed in one step saving process steps and money. Ultra sonic slitting simultaneously cutting and sealing the edges adjacent to the cut is preferred. Ultrasonic slitting can operate at relatively high speeds making it a quick processing step and melts the edges of the cut to form solid plastic edges to eliminate edge penetration of silver halide chemistry solutions.
Preferably, the ultrasonic horn has a frequency of between 18 and 26 Khz. Below 15 Khz, it has been shown that the edges of the cut are not melted completely leaving some of the fabric exposed to edge penetration. A horn frequency over 30 Khz has been shown to give no more advantage in edge penetration than frequencies of between 18 and 26 Khz and it uses more energy and the horn wears out faster and needs to be replaced more frequently.
Preferably, the upper and lower polymer sheets have glass transition temperature differences of less than 15 degrees Celsius. This ensures that when the imaging element is cut and melted that the polymer sheets surrounding the textile melt at the same rate so that there is complete encapsulation of the textile and that there is not waviness or curliness to the edges from different melting rates. The waviness or curliness of the edges can occur when the upper and lower polymer sheet glass transition temperatures are more than 20 degrees Celsius apart.
The textile having a glass transition temperature within 15 degrees Celsius from the upper and lower polymer sheets is preferred. It has been shown that when the glass transition temperature of the textile is within 15 degrees Celsius of the upper and lower polymer sheets, the three layers melt at the same rate and completely seal the imaging element. If the textile has a glass transition temperature over 20 degrees different than the surrounding polymer sheets, incomplete sealing (allowing for edge penetration) can occur or wavy or curly edges can be formed. These wavy or curly edges are unsatisfactory to the consumer.
The layers of the biaxially oriented polyolefin sheet have levels of voiding, TiO2 and colorants adjusted to provide optimum transmission properties. The biaxially oriented polyolefin sheet is laminated to a textile for stiffness for efficient image processing, as well as product handling and display. Further, the thin polyolefin skin layer on the top of the biaxially oriented polyolefin sheet of this invention can be optimized for image receiving layer adhesion. One example is a thin layer of biaxially oriented polycarbonate allows a solvent based polycarbonate dye receiver layer typical of thermal dye transfer imaging to adhere to the base without an expensive primer coating.
Any suitable biaxially oriented polyolefin sheet may be utilized for the upper polymer sheet. Microvoided composite biaxially oriented sheets are preferred because the voids provide opacity without the use of TiO2. Microvoided composite oriented sheets are conveniently manufactured by coextrusion of the core and surface layers, followed by biaxial orientation, whereby voids are formed around void-initiating material contained in the core layer. Such composite sheets are disclosed in, for example, U.S. Pat. Nos. 4,377,616; 4,758,462; and 4,632,869.
The core of the preferred composite sheet should be from 15 to 95% of the total thickness of the sheet, preferably from 30 to 85% of the total thickness. The nonvoided skin(s) should thus be from 5 to 85% of the sheet, preferably from 15 to 70% of the thickness.
The optical properties of the imaging elements in accordance with the invention are improved as the color materials may be concentrated at the surface of the biaxially oriented sheet for most effective use with little waste of the colorant materials. Photographic materials utilizing microvoided sheets and textiles of the invention have improved resistance to tearing. The invention allows faster hardening of photographic paper emulsion, as water vapor is not transmitted from the emulsion through the biaxially oriented sheets.
The photographic elements of this invention utilize a low cost method for printing multiple color branding information of the back side of the image increasing the content of the information on the back side of the image.
The imaging elements of this invention utilize an integral emulsion bonding layer that allows the emulsion to adhere to the support materials during manufacturing and wet processing of images. The microvoided sheets are laminated to the textile utilizing a bonding layer that prevents delamination of the biaxially oriented sheets from the base paper. These and other advantages will be apparent from the detailed description below.
The layers of the upper biaxially oriented polyolefin sheet of this invention have levels of voiding, optical brightener and colorants adjusted to provide optimum optical properties for image sharpness, lightness and opacity. An important aspect of this invention is the voided polymer layer(s) under the silver halide image layer. The microvoided polymer layers in the oriented polyolefin sheet and the textile base provides acceptable opacity, sharpness and lightness without the use of expensive white pigments that is typical with prior art materials. Because the use of white pigments is avoided, the dye hue of color dye couplers coated on the support of this invention is significantly improved yielding an image with snappy color. The preferred percent transmission for the reflective support material of this invention is between 0 and 5%. For a reflective support material, transmission of a significant amount of light is undesirable as light illuminates the logo printing on the back of the image, reducing the quality of the image during viewing. A percent transmission greater than 7% allows enough light to be transmitted during image viewing to reduce the quality of the image.
The upper and lower biaxially oriented polyolefin sheets of the invention are laminated to a textile or fabric core of the invention for stiffness and for efficient image processing as well as consumer product handling. Lamination of high strength biaxially oriented polyolefin sheets to the textile significantly increases the tear resistance of the photographic element compared to present photographic paper core. Because the white pigments have been significantly reduced in the upper biaxially oriented sheet, the textile is required to maintain image opacity to reduce image show through. The biaxially oriented sheets are laminated to the textile with an ethylene metallocene plastomer that allows for lamination speeds exceeding 500 meters/min and optimizes the bond between the textile and the biaxially oriented polyolefin sheets.
The biaxially oriented sheets used in the invention contain an integral emulsion bonding layer which avoids the need for expensive priming coatings or energy treatments. The bonding layer used in the invention is a low density polyethylene skin on the biaxially oriented sheet. Gelatin based silver halide emulsion layers of the invention have been shown to adhere well to low density polyethylene when used in combination with corona discharge treatment. The integral bonding skin layer also serves as a carrier for the blue tints that correct for the native yellowness of the gelatin based silver halide image element. Concentrating the blue tints in the thin, skin layer reduces the amount of expensive blue tint materials when compared to prior art photographic papers that contain blue tint materials.
The backside of the photographic element is laminated with a biaxially oriented sheet to reduce humidity image curl. There are particular problems with prior art color papers when they are subjected to extended high humidity storage such as at greater than 50% relative humidity. The high strength biaxially oriented sheet on the backside resists the curling forces, producing a much flatter image. The biaxially oriented sheet on the back has roughness at two frequencies to allow for efficient conveyance through photographic processing equipment and improved consumer writability as consumers add personal information to the back side of photographic paper with pens and pencils. The biaxially oriented sheet also has an energy to break of 4.0xc3x97107 joules per cubic meter to allow for efficient chopping and punching of the photographic element during photographic processing of images.
Preferred biaxially oriented sheets are disclosed in U.S. Pat. Nos. 5,866,282; 5,888,683; 6,030,742 and 6,040,124. Suitable classes of thermoplastic polymers for the upper and lower biaxially oriented sheet core and skin layers include polyolefins, polyesters, polyarnides, polycarbonates, cellulosic esters, polystyrene, polyvinyl resins, polysulfonamides, polyethers, polyimides, polyvinylidene fluoride, polyurethanes, polyphenylenesulfides, polytetrafluoroethylene, polyacetals, polysulfonates, polyester ionomers, and polyolefin ionomers. Copolymers and/or mixtures of these polymers can be used.
Suitable polyolefins for the core and skin layers of the backside sheet include polypropylene, polyethylene, polymethylpentene, and mixtures thereof. Polyolefin copolymers, including copolymers of propylene and ethylene such as hexene, butene and octene are also useful. Polypropylenes are preferred because they are low in cost and have good strength and surface properties.
Suitable polyesters include those produced from aromatic, aliphatic or cycloaliphatic dicarboxylic acids of 4-20 carbon atoms and aliphatic or alicyclic glycols having from 2-24 carbon atoms. Examples of suitable dicarboxylic acids include terephthalic, isophthalic, phthalic, naphthalene dicarboxylic acid, succinic, glutaric, adipic, azelaic, sebacic, fumaric, maleic, itaconic, 1,4-cyclohexanedicarboxylic, sodiosulfoisophthalic and mixtures thereof. Examples of suitable glycols include ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, 1,4-cyclohexanedimethanol, diethylene glycol, other polyethylene glycols and mixtures thereof. Such polyesters are well known in the art and may be produced by well-known techniques, e.g., those described in U.S. Pat. No. 2,465,319 and U.S. Pat. No. 2,901,466. Preferred continuousmatix polyesters are those having repeat units from terephthalic acid or naphthalene dicarboxylic acid and at least one glycol selected from ethylene glycol, 1,4-butanediol and 1,4-cyclohexanedimethanol. Poly(ethylene terephthalate), which may be modified by small amounts of other monomers, is especially preferred. Other suitable polyesters include liquid crystal copolyesters formed by the inclusion of suitable amount of a co-acid component such as stilbene dicarboxylic acid. Examples of such liquid crystal copolyesters are those disclosed in U.S. Pat. Nos. 4,420,607; 4,459,402; and 4,468,510.
Useful polyamides include nylon 6, nylon 66, and mixtures thereof. Copolymers of polyamides are also suitable continuous phase polymers. An example of a useful polycarbonate is bisphenol-A polycarbonate. Cellulosic esters suitable for use as the continuous phase polymer of the composite sheets include cellulose nitrate, cellulose triacetate, cellulose diacetate, cellulose acetatepropionate, cellulose acetate butyrate, and mixtures or copolymers thereof. Useful polyvinyl resins include polyvinyl chloride, poly(vinyl acetal), and mixtures thereof. Copolymers of vinyl resins can also be utilized.
When using a textile in the base, it is preferable to extrusion laminate the top and bottom biaxially oriented polymer sheets to the textile using a polyolefin resin. Extrusion laminating is carried out by bringing together the biaxially oriented sheets of the invention and the textile base with application of an adhesive between them followed by their being pressed in a nip such as between two rollers. The adhesive may be applied to either the upper or lower biaxially oriented sheets or the textile prior to their being brought into the nip. In a preferred form the adhesive is applied into the nip simultaneously with the biaxially oriented sheets and the textile.
The bonding agent used for bonding biaxially oriented sheets to textile is preferably selected from a group of resins that can be melt extruded at about 160.degree. C. to 300.degree. C. Usually, a polyolefin resin such as polyethylene or polypropylene is used.
Adhesive resins are preferred for bonding upper and lower biaxially oriented sheets to the textile. An adhesive resin used in this invention is one that can be melt extruded and provide sufficient bond strength between the textile and the biaxially oriented sheet. For use in the conventional photographic system, peel forces between the paper and the biaxially oriented sheets need to be greater than 150 grams/5 cm to prevent delamination during the manufacture of the photographic base, during processing of an image or in the final image format. xe2x80x9cPeel strengthxe2x80x9d or xe2x80x9cseparation forcexe2x80x9d or xe2x80x9cpeel forcexe2x80x9d is the measure of the amount of force required to separate the biaxially oriented sheets from the textile. Peel strength is measured using an Instron gauge and the 180 degree peel test with a cross head speed of 1.0 meters/min. The sample width is 5 cm and the distance peeled is 10 cm.
In the case of a silver halide photographic system, suitable adhesive resins must also not interact with the light sensitive emulsion layer. Preferred examples of adhesive resins are ionomer (e.g. an ethylene metharylic acid copolymer cross linked by metal ions such as Na ions or Zn ions), ethylene vinyl acetate copolymer, ethylene methyl methacrylate copolymer, ethylene ethyl acrylate copolymer, ethylene methyl acrylate copolymer, ethylene acrylic acid copolymer, ethylene ethyl acrylate maleic anhydride copolymer, or ethylene methacrylic acid copolymer. These adhesive resins are preferred because they can be easily melt extruded and provide peel forces between biaxially oriented polyolefin sheets and base paper greater than 150 grams/5 cm.
Metallocene catalyzed polyolefin plastomers are most preferred for bonding oriented polyolefin sheets to textile because they offer a combination of excellent adhesion to smooth biaxially oriented polyolefin sheets, are easily melt extruded using conventional extrusion equipment and are low in cost when compared to other adhesive resins. Metallocenes are class of highly active olefin catalysts that are used in the preparation of polyolefin plastomers. These catalysts, particularly those based on group IVB transition metals such as zirconium, titanium, and hafnium, show extremely high activity in ethylene polymerization. Various forms of the catalyst system of the metallocene type may be used for polymerization to prepare the polymers used for bonding biaxially oriented polyolefin sheets to cellulose paper. Forms of the catalyst system include but are not limited to those of homogeneous, supported catalyst type, high pressure process or a slurry or a solution polymerization process. The metallocene catalysts are also highly flexible in that, by manipulation of catalyst composition and reaction conditions, they can be made to provide polyolefins with controllable molecular weights. Suitable polyolefins include polypropylene, polyethylene, polymethylpentene, polystyrene, polybutylene and mixtures thereof. Development of these metallocene catalysts for the polymerization of ethylene is found in U.S. Pat. No. 4,937,299 (Ewen et al).
The most preferred metallcoene catalyzed copolymers are very low density polyethylene (VLDPE) copolymers of ethylene and a C4 to C10 alpha monolefin, most preferably copolymers and terpolymers of ethylene and butene-1 and hexene-1. The melt index of the metallocene catalyzed ethylene plastomers preferable fall in a range of 2.5 g/10 min to 27 g/10 min. The density of the metallocene catalyzed ethylene plastomers preferably falls in a range of 0.8800 to 0.9100. Metallocene catalyzed ethylene plastomers with a density greater than 0.9200 do not provide sufficient adhesion to biaxially oriented polyolefin sheets.
Melt extruding metallocene catalyzed ethylene plastomers presents some processing problems. Processing results from earlier testing in food packaging applications indicated that their coating performance, as measured by the neck-in to draw-down performance balance, was worse than conventional low density polyethylene making the use of metallocene catalyzed plastomers difficult in a single layer melt extrusion process that is typical for the production of current photographic support. By blending low density polyethylene with the metallocene catalyzed ethylene plastomer, acceptable melt extrusion coating performance was obtained making the use of metallocene catalyzed plastomers blended with low density polyethylene (LDPE) very efficient. The preferred level of low density polyethylene to be added is dependent on the properties of the LDPE used (properties such as melt index, density and type of long chain branching) and the properties of the metallocene catalyzed ethylene plastomer selected. Since metallocene catalyzed ethylene plastomers are more expensive than LDPE a cost to benefit trade-off is necessary to balance material cost with processing advantages such as neck-in and product advantages such as biaxially oriented sheet adhesion to the textile. In general, the preferred range of LDPE blended is 10% to 80% by weight.
The preferred stiffness of the imaging element in any direction is between 150 and 300 millinewtons. The bending stiffness of the textile composite base is measured by using the Lorentzen and Wettre stiffness tester, Model 1 6D. The output from is instrument is force, in millinewtons, required to bend the cantilevered, unclasped end of a sample 20 mm long and 38.1 mm wide at an angle of 15 degrees from the unloaded position. A photographic element with stiffness in any direction less than 120 millinewtons can cause transport problems in present photographic processing equipment. Further, photographic element stiffness less than 120 millinewtons is perceived by consumers as low in quality. A photographic element with a stiffness in any direction greater than 330 millinewtons can also cause transport, punching and chopping problems in photographic processing equipment as the stiffness of the photographic element exceeds the capability of present photographic processing equipment.
While melt extrusion polymers are preferred for laminating biaxially oriented polymer sheets to the textile, room temperature adhesive lamination can also be useful. Room temperature adhesive lamination is accomplished by applying an adhesive to either the biaxially oriented polymer sheet or the textile prior to the lamination nip. Suitable adhesives include acrylic pressure sensitive adhesives, UV cure polymer adhesives, and latex based adhesives.
The structure of a preferred photographic base with oriented polyolefin and a textile where the light sensitive silver halide emulsion is coated on the polyethylene layer is as follows. The polymer layers above and below the bonding layers were formed as an integral sheet prior to lamination:
As used herein, the phrase xe2x80x9cphotographic elementxe2x80x9d or xe2x80x9cimaging elementxe2x80x9d is a material that utilizes photosensitive silver halide in the formation of images. The photographic elements can be single color elements, multicolor elements or black and white where there is retained silver after processing of the image. Multicolor elements contain image dye-forming units sensitive to each of the three primary regions of the spectrum. Each unit can comprise a single emulsion layer or multiple emulsion layers sensitive to a given region of the spectrum. The layers of the element, including the layers of the image-forming units, can be arranged in various orders as known in the art. In an alternative format, the emulsions sensitive to each of the three primary regions of the spectrum can be disposed as a single segmented layer.
The photographic emulsions useful for this invention are generally prepared by precipitating silver halide crystals in a colloidal matrix by methods conventional in the art. The colloid is typically a hydrophilic film forming agent such as gelatin, alginic acid, or derivatives thereof.
The crystals formed in the precipitation step are washed and then chemically and spectrally sensitized by adding spectral sensitizing dyes and chemical sensitizers, and by providing a heating step during which the emulsion temperature is raised, typically from 40.degree. C. to 70.degree. C., and maintained for a period of ime. The precipitation and spectral and chemical sensitization methods utilized in preparing the emulsions employed in the invention can be those methods known in the art.
Chemical sensitization of the emulsion typically employs sensitizers such as sulfur-containing compounds, e.g., allyl isothiocyanate, sodium thiosulfate and allyl thiourea; reducing agents, e.g., polyamines and stannous salts; noble metal compounds, e.g., gold, platinum; and polymeric agents, e.g., polyalkylene oxides. As described, heat treatment is employed to complete chemical sensitization. Spectral sensitization is effected with a combination of dyes, which are designed for the wavelength range of interest within the visible or infrared spectrum. It is known to add such dyes both before and after heat treatment.
After spectral sensitization, the emulsion is coated on a support. Various coating techniques include dip coating, air knife coating, curtain coating, and extrusion coating.
The silver halide emulsions utilized in this invention may be comprised of any halide distribution. Thus, they may be comprised of silver chloride, silver bromide, silver bromochloride, silver chlorobromide, silver iodochloride, silver iodobromide, silver bromoiodochloride, silver chloroiodobromide, silver iodobromochloride, and silver iodochlorobromide emulsions. It is preferred, however, that the emulsions be predominantly silver chloride emulsions. By predominantly silver chloride, it is meant that the grains of the emulsion are greater than about 50 mole percent silver chloride. Preferably, they are greater than about 90 mole percent silver chloride; and optimally greater than about 95 mole percent silver chloride.
The silver halide emulsions can contain grains of any size and morphology. Thus, the grains may take the form of cubes, octahedrons, cubo-octahedrons, or any of the other naturally occurring morphologies of cubic lattice type silver halide grains. Further, the grains may be irregular such as spherical grains or tabular grains. Grains having a tabular or cubic morphology are preferred.
The photographic elements of the invention may utilize emulsions as described in The Theory of the Photographic Process, Fourth Edition, T. H. James, Macmillan Publishing Company, Inc., 1977, pages 151-152. Reduction sensitization has been known to improve the photographic sensitivity of silver halide emulsions. While reduction sensitized silver halide emulsions generally exhibit good photographic speed, they often suffer from undesirable fog and poor storage stability.
Reduction sensitization can be performed intentionally by adding reduction sensitizers, chemicals which reduce silver ions to form metallic silver atoms, or by providing a reducing environment such as high pH (excess hydroxide ion) and/or low pAg (excess silver ion). During precipitation of a silver halide emulsion, unintentional reduction sensitization can occur when, for example, silver nitrate or alkali solutions are added rapidly or with poor mixing to form emulsion grains. Also, precipitation of silver halide emulsions in the presence of ripeners (grain growth modifiers) such as thioethers, selenoethers, thioureas, or ammonia tends to facilitate reduction sensitization.
Examples of reduction sensitizers and environments which may be used during precipitation or spectral/chemical sensitization to reduction sensitize an emulsion include ascorbic acid derivatives; tin compounds; polyamine compounds; and thiourea dioxide-based compounds described in U.S. Pat. Nos. 2,487,850; 2,512,925; and British Patent 789,823. Specific examples of reduction sensitizers or conditions, such as dimethylamineborane, stannous chloride, hydrazine, high pH (pH 8-11) and low pAg (pAg 1-7) ripening are discussed by S. Collier in Photographic Science and Engineering, 23, 113 (1979). Examples of processes for preparing intentionally reduction sensitized silver halide emulsions are described in EP 0 348 934 A1 (Yamashita), EP 0 369 491 (Yamashita), EP 0 371 388 (Ohashi), EP 0 396 424 A1 (Takada), EP 0 404 142 A1 (Yamada), and EP 0 435 355 A1 (Makino).
The photographic elements of this invention may use emulsions doped with Group VIII metals such as iridium, rhodium, osmium, and iron as described in Research Disclosure, September 1994, Item 36544, Section I, published by Kenneth Mason Publications, Ltd., Dudley Annex, 12a North Street, Emsworth, Hampshire PO10 7DQ, ENGLAND. Additionally, a general summary of the use of iridium in the sensitization of silver halide emulsions is contained in Carroll, xe2x80x9cIridium Sensitization: A Literature Review,xe2x80x9d Photographic Science and Engineering, Vol. 24, No. 6, 1980. A method of manufacturing a silver halide emulsion by chemically sensitizing the emulsion in the presence of an iridium salt and a photographic spectral sensitizing dye is described in U.S. Pat. No. 4,693,965. In some cases when such dopants are incorporated, emulsions show an increased fresh fog and a lower contrast sensitometric curve when processed in the color reversal E-6 process as described in The British Journal of Photography Annual, 1982, pages 201-203.
A typical multicolor photographic element of the invention comprises the invention laminated support bearing a cyan dye image-forming unit comprising at least one red-sensitive silver halide emulsion layer having associated therewith at least one cyan dye-forming coupler; a magenta image-forming unit comprising at least one green-sensitive silver halide emulsion layer having associated therewith at least one magenta dye-forming coupler; and a yellow dye image-forming unit comprising at least one blue-sensitive silver halide emulsion layer having associated therewith at least one yellow dye-forming coupler. The element may contain additional layers, such as filter layers, interlayers, overcoat layers, subbing layers, and the like. The support of the invention may also be utilized for black-and-white photographic print elements.
The photographic elements may also contain a transparent magnetic recording layer such as a layer containing magnetic particles on the underside of a transparent support, as in U.S. Pat. Nos. 4,279,945 and 4,302,523. Typically, the element will have a total thickness (excluding the support) of from about 5 to about 30 .mu.m.
The elements of the invention may use materials as disclosed in Research Disclosure 40145, September 1997, particularly the couplers as disclosed in Section II of the Research Disclosure.
In the following Table, reference will be made to (1) Research Disclosure, December 1978, Item 17643, (2) Research Disclosure, December 1989, Item 308119, and (3) Research Disclosure, September 1994, Item 36544, all published by Kenneth Mason Publications, Ltd., Dudley Annex, 12a North Street, Emsworth, Hampshire PO10 7DQ, ENGLAND. The Table and the references cited in the Table are to be read as describing particular components suitable for use in the elements of the invention. The Taole and its cited references also describe suitable ways of preparing, exposing, processing and manipulating the elements, and the images contained therein.
The photographic elements can be exposed with various forms of energy which encompass the ultraviolet, visible, and infrared regions of the electromagnetic spectrum, as well as with electron beam, beta radiation, gamma radiation, X ray, alpha particle, neutron radiation, and other forms of corpuscular and wave-like radiant energy in either noncoherent (random phase) forms or coherent (in phase) forms, as produced by lasers. When the photographic elements are intended to be exposed by X rays, they can include features found in conventional radiographic elements.
The imaging elements of this invention can be exposed by means of a collimated beam, to form a latent image, and then processed to form a visible image, preferably by other than heat treatment. A collimated beam is preferred as it allows for digital printing and simultaneous exposure of the imaging layer on the top without significant internal light scatter. A preferred example of a collimated beam is a laser also known as light amplification by stimulated emission of radiation. The laser is preferred because this technology is used widely in a number of digital printing equipment types. Further, the laser provides sufficient energy to simultaneously expose the light sensitive silver halide coating on the top of the display material of this invention without undesirable light scatter. Subsequent processing of the latent image into a visible image is preferably carried out in the known RA-4.TM. (Eastman Kodak Company) Process or other processing systems suitable for developing high chloride emulsions.